lowering salt intake in chronic kidney disease: a pilot randomized crossover trial

Conditions: Kidney Disease

Summary: abstract background: it is well recognized that excess dietary salt intake plays a major role in the development of hypertension. chronic kidney disease (ckd) is associated with excess salt and water retention (excess volume) which is associated with hypertension. hypotheses: hypothesis 1: dietary salt restriction will improve volume status in subjects with ckd stages 3-4 as assessed by bioelectrical impedance analysis (bia). hypothesis 2: dietary salt restriction will result in improved blood pressure control in patients with ckd stages 3-4. hypothesis 3: dietary salt restriction will decrease albuminuria in patients with ckd stages 3-4. patients and trial design: this randomized crossover pilot study is designed to assess the effect of salt restriction on volume status in patients with ckd stages 3 and 4. subjects will be randomized to a treatment order: (1) 4 weeks of salt restriction of \<85 mmol sodium per day, a 2 week washout period, and 4 weeks of usual salt diet, or (2) 4 weeks of usual diet, 2 weeks washout, and 4 weeks of salt restriction. patients will receive dietary counseling in person at each study visit and at weekly intervals by phone calls from study dieticians. at weeks 0, 4, 6 and 10, patients will undergo assessments for (i) physical examination with assessments for weight, blood pressure, pulse, anthropometrics and a standardized clinical assessment of volume status. (ii) volume status using bioelectrical impedance analysis (bia) (iii) 24-hour urine testing for, albumin, creatinine and aldosterone every 2 weeks throughout the study, a 24-hour urine sodium will be measured for compliance, and serum electrolytes will be assessed for safety. data analysis: bia measurements in the low salt group will be compared with the regular diet group using the standard linear model analysis for 2x2 crossover trials. additionally, 24-hour ambulatory and static blood pressure and 24-hour urine aldosterone levels will be compared between the two groups. future implications: a significant reduction in the degree of volume expansion (as assessed by bia) and blood pressure as a result of a salt restricted diet would have implications for renal and cardiovascular protection and would warrant confirmation by a larger randomized trial.


Eligibility criteria:
inclusion criteria: individuals eligible to participate in this study must meet all of the following criteria: * willing and able to provide written, signed informed consent after the nature of the study has been explained, and prior to any research-related procedures. * age ≥ 18 years and ≤ 85 years. * willing and able to comply with all study procedures. * patients with egfr of 20 to 60 ml/min/173m2 by the abbreviated (4-variable) mdrd equation and a relatively stable clinical course. * sitting systolic blood pressure ≥ 100 mmhg prior to study entry (to exclude people at risk from hypotension from dietary salt reduction). exclusion criteria: individuals who meet any of the following exclusion criteria will not be eligible to participate in the study: * recent acute illness (≤1 month). minor ailments such as a recovered common cold or allergic rhinitis would not be considered as exclusion criteria but would be left to the site pi's discretion. * recent hospitalization (≤1 month) unless clearly for a minor elective procedure unlikely to interfere with bia measurements. the final decision will be left to the site pi's discretion. * any psychological condition (including alcoholism) that could interfere with the patient's ability to comply with the study protocol. * subjects with baseline 24-hour urinary sodium excretion ≤100 mmol/day. * amputation of a limb other than fingers or toes. * pacemaker, defibrillator, implantable pump, artificial joint, pins, plates or other types of metal objects in the body (other than dental fillings). * coronary stents or metal suture material in the heart. * use of any investigational product or investigational medical device within 30 days prior to screening, or requirement for any investigational agent prior to completion of all scheduled study assessments. * weight over 300 pounds (limitation for examination table). * pregnancy or lactation. * patients with kidney diseases known to be associated with salt wasting (see above). * patients with atrial fibrillation as ambulatory blood pressure measurements may not be accurate in this setting. * any condition that, in the view of the pi, places the subject at high risk of poor treatment compliance or of not completing the study.

Keywords: kidney disease albuminuria glomerular filtration rate volume status bioimpedance analysis